Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. Aftershocks Threaten Effort to Rescue Girl Found Alive in Mexico Quake Rubble by VOA News Rescue teams in central Mexico continued to work Thursday to reach those still trapped inside the dozens of buildings that fell during a massive earthquake Tuesday that killed more than 230 people. One search in Mexico City took place at a school where workers spotted a girl Wednesday buried in debris and were able to confirm she was still alive by asking her to move her hand. That rescue effort took on a heightened sense of urgency Thursday as the threat of aftershocks increased the possibility the unstable three-story structure could collapse. Rescuers took extra precautions and meticulously worked to avoid shifting the unstable pile of rubble surrounding the girl. "The girl told us her name, Frida," rescue worker Rodolfo Ruvalcava told FORO TV. "Apart from just her name, she told us there were two other kids, and that there were other bodies. We don't know if the others are alive." 5,000 schools damaged Since the 7.1 magnitude earthquake struck, workers at the school have found 26 people dead there, including 21 children. The school was one of more than 5,000 schools damaged by the earthquake, according to Mexico's education secretary. President Enrique Pena Nieto said at least 50 people had been pulled alive from buildings in Mexico City. He declared three days of mourning for those who had died and expressed the country's condolences to their families and friends. He also praised Mexicans' rapid response to the disaster, while stressing the priorities remained saving lives and getting medical attention to those in need. "I need to recognize the volunteers who are unconditionally helping those who need it," Pena Nieto said. "Once again, Mexicans have demonstrated that the strength of solidarity is much greater," the president's office posted in a tweet that included a video showing thousands of people involved in relief efforts. Help from abroad In addition to the local response in Mexico City and the states of Morelos, Puebla, Mexico, Guerrero and Oaxaca, help was coming from other nations. The U.S. Agency for International Development on Thursday sent more than 60 disaster responders and tools and medical equipment to Mexico City. "They'll be working closely with Mexican disaster authorities to help rescue earthquake survivors and assess structures for earthquake damage," said USAID Administrator Mark Green. A 32-member search-and-rescue team from Panama arrived with two dogs Wednesday. The Israeli military said it would send 70 people to help with rescue efforts by providing engineering assistance. Pena Nieto said his government had also accepted the technical and specialized help offered by Spain, Japan and other Latin American countries that have experienced similar disasters. Mexico City's international airport sustained some structural damage, but Pena Nieto said the airport had returned to normal operations. Loss of communications Canadian travel blogger Mike Corey was in Mexico City when the earthquake hit. The scariest part of the ordeal, he said, was the loss of cell reception, "which is not good if you're trapped underneath things." "I guarantee that cost lives, because someone's there, they can't contact anybody and they're trapped under rubble," he said. Pope Francis acknowledged earthquake victims during an open prayer Wednesday in St. Peter's Square, saying he wanted to "express my closeness and prayer to the dear Mexican people." IN PHOTOS: Crews in Mexico City Search for Quake Victims The quake hit less than two weeks after another earthquake killed more than 90 people in the country's south. The U.S. Geological Survey said the two quakes appeared to be unrelated. The earthquake struck exactly 32 years after an 8.0 temblor killed nearly 10,000 people in and around Mexico City. VOA's Victor Beattie, Steve Miller and Celia Mendoza contributed to this report.